In general, in a state where detergent, wash water and laundry are put into a tub and a drum installed on the same level, a washing machine washes the laundry by using friction between the laundry and the drum rotated by driving force of a motor. The washing machine provides washing effects such as beating and rubbing without damaging or tangling the laundry.
Normally, tap water is used as the wash water and supplied into the tub and the drum with the detergent, for washing the soiled laundry. Calcium of the tap water and a surfactant of the detergent react with each other, thereby to generate insoluble metal soap. The metal soap easily sticks to the inner wall of the drum. It more frequently occurs in powder detergent containing high fatty acid sodium.
The metal soap remaining in the laundry sticks to fiber remnants or dirties separated from the laundry and absorb moisture, thereby to propagate microorganisms. In addition, the metal soap elements may generate floccules causing rot, and may also generate molds causing bad smell. Furthermore, the molds are grown to float in the water and stick to the laundry in the washing process. As a result, even if the soiled laundry is washed, it does not mean that the laundry is sanitary.
Various germs existing in the air such as Staphyllococcus aureus, Bacillus cereus and Atypical mycobacterium are easily adhered to clothes while being clothed. Even after the clothes are washed by the washing machine, such germs still remain in the clothes. Especially, if the clothes are not sufficiently dried, the remaining germs propagate themselves, generate unpleasant smell and discolor the clothes. If sick persons, babies or children having weak immunity wear the clothes in which the germs remain, they may have health problems like a skin disease.